Doors having compression molded door skins are well known in the art. Attempts have been made to provide a textured pattern on the exterior of the door skin to simulate the grain of natural wood. One such attempt provides a printed wood grain pattern on the door skin. However, the printed pattern has no depth or texture, as found in natural wood. The variable depth and texture found in natural wood provides a surface amenable to stain or other finishing. Therefore, staining and/or finishing is not possible with printed door skins. Furthermore, the print ink fails to simulate crisp wood grain ticks, and tick and background tonal variations.
Another attempt to simulate a natural wood grain pattern in the exterior surface of the door skin provides for transferring a photographic image of the grain pattern into an embossing plate, by an etching process, to form a lower surface with raised ridges extending therefrom in the embossing plate. Etching is a process whereby areas of a metal plate are covered with an acid resistant ground and an acid or mordant solution is applied to the plate. The areas that have no resistant ground are eaten away by the acid. An image or pattern is etched into the metal plate that then has a lower surface and a raised surface. Thus, the resistant ground, or “resist”, controls where and how the acid eats into the metal plate. Chromed steel, copper and zinc are three most common metals used for embossing plates. Chromed steel is the hardest of the three metals, and will not wear down as quickly as non-steel plates after repeated embossing.
Different acids are necessary for etching different metals. In addition, there are different resists and ways of applying the resists. There are also various ways to expose the metal to the acid after the resist has been applied so that tone and texture can be created. Acid treatment of the plate then etches out the uncoated metal, creating a textured surface in the embossing plate. Raised lines or ridges are created by etching into the plate around lines of protective resist. The acid then eats away at the unprotected portions of the metal plate, leaving the raised lines or ridges. These lines create the illusion of wood grain ticks. The height of the lines is controlled by the width of the corresponding line of resist that is removed.
Conventional etched plates may be used as an embossing plate or with a molded die set, for embossing and forming a molded article having the pattern on its exterior surface. As known in the art, the pattern may be formed in the article's surface by embossing or using a molded die set, and subjecting a substrate to selected amounts of heat, pressure and time to form the molded article. When embossing a substrate to form a door skin having a wood grain pattern, the embossing plate is pressed into the material to provide bundles of wood ticks that form the grain pattern on the resulting door skin surface. A wood grain pattern is a cluster or bundle of spaced, raised lines of metal, or “ticks”, which extend in a pattern simulating the appearance of wood. The ticks must be carefully spaced to simulate a natural wood grain.
During etching, it is often difficult to achieve clear, crisp wood ticks because as the acid eats into the metal around the ticks, thereby forming gaps, it also eats into the side walls of the ticks. If adjacent gaps (defining a tick therebetween) are too closely spaced, the acid may simply eat away at, and destroy the tick. As such, conventional etched plates having wood grain patterns do not emboss highly realistic wood ticks. In addition, such conventional etched plates often have sharp edges on the upper portions of the ticks, and undercuts at the bases of the gaps due to the nature of the etching process. If the gaps are etched too deep, undercutting often results since the acid has longer to eat away at the side walls of adjacent ticks as the gaps get deeper, as compared to etching shallower gaps that do not require as much exposure time to the acid.
In addition, conventional door skins with embossed wood grain patterns fail to capture the subtle wood tone variations found in natural wood. Natural wood includes not only wood ticks, but varying background tones as well. It is the background tones and sharp, crisp ticks found in natural wood that provides the aesthetically appealing appearance, and that enables it to be easily stained or finished. Conventional embossing plates used to form door skins with wood grain patterns fail to capture both naturally appearing wood ticks and wood tones. If the door skin surface is stained, it does not appear realistic. As commonly known in the art, stains include a dye or pigment in solution, and are generally used to color a wood by penetrating the wood surface. As such, the natural wood tones and ticks may be enhanced or colored, without marring the wood surface textures and tones, as with paint.
Stains do not penetrate the surface of a composite or polymeric door skin in the same manner as natural wood. Therefore, attempts to stain a composite or polymeric door skin for purposes of enhancing tones and ticks is a difficult process for a typical consumer. The stain may not simply be applied with a brush or rag, and the excess wiped off, as can be done with natural wood. Rather, such door skins typically require multiple applications of stain, which must then be selectively removed by hand. This technique often requires a professional or one experienced in staining in order to capture a natural wood appearance. Alternatively, portions of the door skin surface may be highlighted by spray gun application of the stain, or other shading material. The door skin surface may be evenly sprayed, resulting in an unnatural, monotone appearance. Even if the stain is carefully applied in specific areas, the resulting tones and wood ticks may appear splotchy and unrealistic if careful highlighting is not achieved. The average homeowner or consumer is not sufficiently skilled to stain or finish such a molded door skin, and achieve a realistic wood grain appearance using commercial stain finishing products.
Therefore, there is a need for a molded door skin having a wood grain pattern that may be easily stained, and that precisely captures both the wood ticks and wood tones found in natural wood grain.